1. Field of the Invention
This invention relates to a method for manufacturing fine powder of barium zirconate, BaZrO.sub.3.
2. Description of the Prior Art
In recent years, manufacture of super fine powder or particles of BaZrO.sub.3 has been demanded from various fields. One of the field is concerned with multilayer ceramics. In capacitors, it is desirable that they are small in size and light in weight similar to other electronic parts, coupled with high capacitance. For the purposes, attention has been drawn to multilayer ceramic capacitors, which make use of BaZrO.sub.3 as a dielectric material. In order to provide a thin and uniform layer of the material, formation of super fine powder of BaZrO.sub.3 is demanded. For the manufacture of the multilayer ceramic capacitor, lead is ordinarily incorporated so as to improve the firing property and temperature characteristics. If too high a firing temperature is used, part of the lead is evaporated. Thus it becomes difficult to obtain a multilayer ceramic capacitor of uniform characteristics. In this connection, finer powder of BaZrO.sub.3 permits lower firing temperatures and thus it is needed to make super fine powder of BaZrO.sub.3.
Super fine powder of BaZrO.sub.3 is very desirous as an electrostrictive or piezoelectric material because of improvements of characteristics. Super fine powder of BaZrO.sub.3 is also effective for use as a transparent ceramic material. This is because, as described above, if the powder size is smaller and more uniform, lower firing temperatures can be expected.
As is well known in the art, it is the usual practice to manufacture BaZrO.sub.3 by solid phase reaction. In the reaction, barium carbonate (BaCO.sub.3) and zirconium oxide, both in powder form, are mixed in a ball mill and subjected to the solid phase reaction at a temperature of 1400.degree. to 1500.degree. C. Thereafter, the reaction product is mechanically milled. Accordingly, the powder size is relatively large and is not uniform. In addition, BaZrO.sub.3 is so hard as aluminium oxide, by which it takes a long time for the milling such as in a ball mill, leading to undesirable incorporation of impurities.
In recent years, attempts have been made to prepare fine powder of BaZrO.sub.3 from metal alkoxides. However, this method is high in production cost and has not been put into practice yet.